SCR Catalyst Deposit Estimation via NOx Sensor Feedback
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Solution Overview
Problem
Existing exhaust aftertreatment systems for internal combustion engines face challenges in accurately estimating reductant deposits, leading to inefficient catalytic conversion and premature aging of the SCR catalyst due to frequent high-temperature regeneration events.
Innovation Solution
A system and method that estimate reductant deposits based on NOx gas measurements upstream and downstream of the SCR unit and the amount of reductant injected, using equations to calculate deposit formation and adjust reductant injection accordingly, while also considering ammonia slip and catalytic conversion efficiency to reduce unnecessary regeneration events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high temperature regeneration events are performed to remove reductant deposits, then the reductant deposits are removed and catalytic conversion efficiency is restored, but the SCR catalyst ages prematurely and its active life is reduced
Solution Approach 1:
The system performs preliminary estimation of reductant deposit amounts using NOx sensor measurements and reductant injection data before regeneration is needed. This allows the control system to predict deposit accumulation and schedule regeneration only when necessary, preventing premature high-temperature events that would age the catalyst.
Solution Approach 2:
The system continuously monitors NOx levels upstream and downstream of the SCR unit, along with reductant injection amounts, to provide feedback on actual catalytic conversion efficiency and deposit formation. This feedback loop enables dynamic adjustment of regeneration timing and intensity, optimizing the balance between maintaining efficiency and preserving catalyst life.
2Reliability
If reductant is continuously injected to maintain catalytic conversion efficiency, then NOx reduction performance is maintained, but reductant deposits accumulate on sidewalls and components
Solution Approach 1:
The control system uses feedback from NOx sensor readings and reductant injection data to estimate deposit formation in real-time. This allows the system to adjust reductant injection rates dynamically, maintaining efficient NOx conversion while minimizing excess reductant that would form deposits.
Solution Approach 2:
The system changes operational parameters such as reductant injection rate and timing based on estimated deposit levels and actual conversion efficiency. By modulating these parameters, the system maintains optimal performance while reducing conditions that lead to excessive deposit accumulation.
3Reliability
If the amount of reductant injected is increased to compensate for deposit formation, then catalytic conversion efficiency is maintained, but more reductant is consumed and deposits may form faster
Solution Approach 1:
The system monitors actual NOx conversion performance and reductant consumption together with estimated deposit levels. This comprehensive feedback allows the control system to distinguish between efficiency losses due to deposits versus other factors, injecting reductant only when truly necessary and at optimal rates.
Solution Approach 2:
The system replaces simple mechanical reductant injection control with an intelligent control system that uses sensor data and estimation algorithms. This substitution enables precise optimization of reductant usage, maintaining efficiency while minimizing consumption and preventing accelerated deposit formation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for accurate estimation and reduction of reductant deposits, inhibiting the formation of hard deposits and minimizing high-temperature regeneration events, thereby extending the life of the SCR catalyst and improving system efficiency.
Implementation Method 1
a SCR catalyst formulated to decompose constituents of the exhaust gas such as nitrous/nitric oxides (NOx) gases in the exhaust gas in the presence of a reductant
Implementation Method 2
reductant deposits accumulate on sidewalls or components of the aftertreatment system
Implementation Method 3
High temperature regeneration events are generally performed to remove these reductant deposits
Data Source
AI summary
An aftertreatment system comprises a selective catalytic reduction (SCR) unit, a reductant injector configured to insert reductant into the aftertreatment system, a first NOx sensor configured to measure an amount of NOx gases at a location upstream of the reductant injector, and a second NOx sensor configured to measure an amount of NOx gases at a location downstream of the SCR unit. A controller is programmed to estimate an amount of reductant deposits formed in the aftertreatment system based on at least the amount of NOx gases measured at the location upstream of the reductant injector, the amount of NOx gases measured at the location downstream of the SCR unit, and an amount of reductant that has been inserted into the aftertreatment system. The controller adjusts an amount of reductant to be inserted into the aftertreatment system based on the estimated amount of reductant deposits formed in the aftertreatment system.